After Hibernating Thirty Years, These “Bears” Reproduce

Could you imagine waking up after a thirty-year slumber, only to eat and reproduce? For a couple of tardigrades, it was reality.

Tardigrades (Acutuncus antarcyticus), also known as “water bears” or moss piglets are found in the rugged Antarctic. These microscopic creatures resemble miniature bears with chubby bodies, stubby legs, claws for walking and climbing. They are only a half a millimeter long on average and are virtually indestructible.

A Tardigrade

The durable animals can withstand temperatures from minus 458 degrees Fahrenheit to a hot 300 degrees. They have also been sent to outer space, where they survived a week where neither radiation nor depressurization affected them.

They can also live without water, undergoing a process called anhydrobiosis. A sugar, trehalose, replaces lost water in their cells. They curl up into a little ball and essentially hibernate.

A new study led by Megumu Tsujimoto, a researcher at the National Institute of Polar Research proved that after decades in freezing conditions, without sustenance, tardigrades can reproduce.

Tsujimoto’s team wrote,

In the available studies of long-term survival of micrometazoans, instances of survival have been the primary observation, and recovery conditions of animals or subsequent reproduction are generally not reported.

Two full-grown tardigrades and one tardigrade egg were collected from Antarctica’s Yukidori Valley on November 6, 1983. They were put on ice, at minus 20 degrees Celsius (minus 4 degrees Fahrenheit) for over thirty years, left in suspended animation. In May of 2014, Tsujimoto’s team thawed them out in a Petri dish.

Tardigrades with Chips of Moss in a Petri Dish

After six days, the tardigrades began to eat algae and the rehydrated egg sample hatched a healthy tardigrade larva. Within three weeks, the female tardigrade and her offspring laid eggs via parthenogenesis (asexually), though tardigrades may reproduce asexually or sexually. The second frozen tardigrade, unfortunately, did not fare as well and died a short time after.

Tardigrades are not true extremophiles because they are not adapted to live in extreme conditions. They can merely survive exposure to such conditions. The longer they undergo such exposure, the greater their chances of dying. Tardigrades are always waiting for something better.

Tardigrades have something in common with humans. After awakening from a deep sleep, they seek food and sex. They are also waiting for something better.